This sounds like a normals issue. Faces can only be textured from one side. In edit mode, select your model and click "recalculate normals". This might/might not work, so if it doesn't you'll need to manually flip the normals of the model yoruself.

It could also be a positioning issue in which case you'll need to make sure the bone rig was applied properly (and not rotated/moved in some weird angle/position).

Many thanks friend! That was exactly the issue.